The cortical processing of visual form in area V1 of the macaque will be investigated to learn how information represented in the thalamic output is re-organized during the initial stages of cortical processing. Isodipole textures and related novel visual stimuli will be exploited to isolate intracortical feature extraction, and to separate this process from spatial filtering. Neural responses will be monitored via field potentials, multi-unit activity, and single-unit activity. Neural activlty will be analyzed in a manner which will detect not only changes in mean firing rate phase-locked to the stimulus, but also more subtle stimulus-linked changes, such as alterations in correlation structure. The first subproject is an analysis of the distribution of form processing in VI, with particular emphasis on its relationship to the columnar organization, laminar organization, and cytochrome oxidase blobs. The second subproject is a detailed analysis of cortical computations related to form processing. As a starting point, this investigation will be organized around a working model developed from human evoked-potential and psychophysical studies, in which the outputs of local nonlinear subunits are combined in a cooperative fashion. This model will be refined or revised on the basis of single-cell responses. Within this model framework, the relationship of the spatial, temporal, and chromatic properties of the subunits will be determined. Visual information processing is considered to be a model for sensory information processing in general. Analysis of the processlng of form, and its relationship to the processing of color and motion, allows us to study feature extraction and cross-modality interactions in a context in which specific hypotheses may be proposed and models may be tested.